Apparatus for simultaneous flush cleaning mixing chambers

ABSTRACT

In machines for spraying plastics, there is a risk that the spray head may be blocked by curing plastic mixture if the head with its mixing chamber is not carefully cleaned as soon as a spraying cycle is completed. The present invention eliminates this risk by an apparatus for flush cleaning the spray head by means of a cleaning liquid which is injected in the head, with said injection being controlled by means of valves also controlling the mixing and spraying of the plastic.

United States Patent 1 1 Svensson 5] Apr. 23, 1974 [54] APPARATUS FORSIMULTANEOUS FLUSH. 3,219,273 11/1965 Killen 239/104 UX L N MIXINGCHAMBERS 3,386,461 6/1968 Fisher 251/207 X 3,558,051 1/1971 Strickler239/1 Inventor: Sven Rolf Svensson, Stenungsund, 3,572,366 3/1971Wiggins 239/112 x Sweden 3,653,594 4/1972 Bok et a1. 239/112 X [73]Assignee: svenska Aktiebolaget Plastic 3,672,570 6/1972 Scarbrough et a1239/112 X Protection, Goteborg, Sweden [22] Filed: July 17, 1973 PrimaryExaminer-Robert S. Ward, Jr. pp NO: 379,983 Attorney, Agent, orFirm-Holman & Stern Related US. Application Data [62] Division of Ser.No 136,666, April 23, 1971, Pat.

No. 3,752,398. [57] ABSTRACT Foreign Application r y Data In machinesfor spraying plastics, there is a risk that Apr. 27, 1970 Sweden 5836/70the spray head may beblocked by curing plastic mixture if the head withits mixing chamber is not care- [52] US. Cl 239/112, 137/15, 134/18fully cleaned as soon as a spraying cycle is completed. [51] Int. ClB05b 15/02, B08b 7/04 The present invention eliminates this risk by anappa [5 Field of S e r c h 239/1, 104, 106, 112; ratus for flushcleaning the spray head by means of a m mwyfl 134/18; 264/39; 251/207;cleaning liquid which is injected in the head, with said 137/15, 625.19,625.22 injection being controlled by means of valves also controllingthe mixing and spraying of the plastic. [5 6] References Cited UNITEDSTATES PATENTS 5/1964 Harban 137/15 2 Claims, 7 Drawing Figures PATENTEDAPR 2 3 m4 sum 1m 2 APPARATUS FOR SIMULTANEOUS FLUSH CLEANING MIXINGCHAMBERS This application is a division of my co-pending applicationSer..No. 136,666 filed Apr. 23, 1971, now Pat. No. 3,752,398.

BACKGROUND OF THE INVENTION The present invention relates to anapparatus for simultaneously flush cleaning mixing chambers in thespraying head of machines for homogenizing and spraying reactiveadditive plastics having a short inductive period.

The creation of two-component systems of monomer synthetic plastics,preferably without solvents, which, upon addition and homogenizationwithout the supply of heat, spontaneously polymerize into nonreversibleduro-plastics of, for instance, epoxy-or urethane type has founded aneed of practically usable apparatus for applying these materials,primarily by spraying.

These materials are already of great importance as surface layers forsealing and reinforcing concrete, primarily in the form of floorings,and as corrosion protectives for steel. Due to their rather viscousnature, the materials are difficult to apply on vertical surfaces inthick layers as it is difficult to give them a desired thixotrope naturein order to prevent dripping. This drawback is largely eliminated if thepolymerization is advanced so fast that the material will set before anydripping has taken place.

Due to the very short period of time, often only some seconds, whichelapses after the material components have been mixed and homogenizeduntil the polymerization has advanced so far that the flowing materialchanges to a rigid product, it is necessary to be able to quickly cleanthe members of the apparatus which have come into contact with thehomogenized (activated) material, at the end of each spraying cycle.This has hitherto been carried out by separate manual activation ofrotary or pressure valves, whereby cleaning liquid followed by air orcleaning liquid and air together have been caused to flush through themixing chamber, etc. Other functions such as starting and stopping themixing motor for the mixing chamber, opening and shutting off air foratomizing the homogenized materials and in certain cases stopping andstarting the driving motors for dosing pumps have also been operatedmanually, often with separate controls located at different portions ofthe machine.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will hereinafter befurther described in connection to a spraying machine shown in theaccompanying drawings.

.FIG. 1 shows mixing head forming part of the machine,

FIG. 2 is a view along line II-II in FIG. 1,

FIGS. 3 and 4 show a section along line A A in FIGS. 1 and 2 in which arotary valve included in the mixing head is in shut and open positionsrespectively,

FIGS. 5 and 6 show sections according to FIGS. 3 and 4 along line B B inFIGS. 1 and 2, and

FIG. 7 shows schematically a complete view of the connections of themachine.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIGS. 1 and 2 is shown a mixinghead 1 provided with two rotary valves 2, which are simultaneouslyactuated by means of a manually operable lever 3. The mixing head isprovided with a mixing motor 4 which causes mechanical stirring of theresin components. The mixing head is further provided with an opening 5leading to the spray nozzles. As can be seen from FIG. 2, the mixinghead is also provided with a number of additional openings which arecontrolled by means of the rotary valves 2. Openings Al and A2 are forthe delivery of resin components to the mixing head. A3 is an openingfor the cleaning liquid, while B1, B2, and B3 are openings forpressurized air.

FIG. 3 which is a section along line A A in FIGS. 1 and 2 shows themixing head 1 when the lever 3 is in the closed position. Hence, thepassages A1 and A2 are closed, while the passage A3 is open, therebyallowing the cleaning liquid to reach the mixing chamber 6 in the mixinghead.

In FIG. 4, the lever 3 has been moved to the opened sage-A3 is closed.

In FIG. 5, the mixing head is shown is closed position in a sectionalong line B B of FIGS. 1 and 2. The passages B1 and B3 are closed whileB2 is .open to the surrounding atmosphere.

FIG. 6 shows a similar view in which the lever 3 is set to the openposition. Passages B1 and B2 are interconnected and passage B3, whichdelivers pressurized air to the mixing head for atomizing the mixture,is opened.

FIG. 7 finally illustrates an embodiment of the entire machine with itsconnections shown schematically. The machine is' primarily driven by anair compressor 7, whichis directly connected to openings B1 and B3 ofthe mixing head 1. The air compressor delivers air for driving themixing motor 4 via a valve 8. The compressor is further, via a reversingvalve 9, connected to an air cylinder 10, which is mechanicallyconnected to and operates a pump 11 for the cleaning liquid.

The liquid pump 11 is connected to openings A3 via a line including anon-return valve 12. The compressed air supplied to opening B1 is, whenthe valve 2 is opened, transferred via passages B1 B2 to the reversingvalve 9, whereby the valve 9 is set in a position in which thecompressed air from the compressor charges the air cylinder 10. Thepiston of this cylinder thereby makes a linear movement, whereby thepiston of the cleaning liquid pump 11 is charged with cleaning liquiddelivered via a line including a non-return valve 13. The compressed airfrom B2 also actuates a switch 14, which starts an'electric motor 15.This motor drives, via speed variators (not shown), two dosing pumps 16which supply openings Al and A2 with the resin components. At the startof the spraying operation, the cleaning liquid pump then isautomatically filled with a cleaning liquid.

When the spraying operation is completed, the lever 3 is set to the shutposition; The passages A1 and A2 are thereby closed, passage A3 opened,passages B1 and B3 closed, and passage B2 is purged. As passage B2 ispurged, the reversing valve 9 is, due to spring actuation, set in a newposition in which the switch 14 is switched off, thereby turning off themotor 15 and the of this cylinder thereby makes a stroke so that thecleaning liquid from pump 11 is injected in the mixing chamber viapassage A3.

The mixing motor 4 is not stopped at the same time as the dosing pumps16 but continues to rotate during the beginning of the flush cleaningoperation due to a delayed closing impulse, which is controlled by acircuit 17 actuating the valve 8. The mixing motor 4 thereby improvesthe cleaning effect, and the flush cleaning then automatically takesplace as soon as the spraying operation is completed.

SUMMARY OF THE INVENTION The purpose of the present invention is toprovide a machine having a reliable function and a simplifiedmaneuvering of all functions necessary for dosing, homogenizing andatomizing the material and for the immediate cleaning of the sprayingnozzle after each spraying cycle by means ofa simultaneous centraloperation from the spray head. Due to this, it is sufficient for theoperator to make one single manipulation at the beginning and at the endrespectively of each spraying cycle so that the operator can concentratehis attention to the spraying work, and his position while working onscaffoldings,etc. The risk of blocking or damaging the spray head due tofailing cleaning is also eliminated.

The apparatus according to the invention is characterized in that acleaning'liquid immediately upon the end of the spraying cycle isinjected into the mixing chamber of the spray head from a pneumaticallydriven pressure increasing pump on a servo impulse from rotary valves,which are mounted in the spray head and which also control otherimportant functions, whereby the mixing chamber and adjacent members foratomizing the spraying media are cleaned from a reactive (monomer)plastic mixture, and that the pump is refilled by a servo impulse at thebeginning of the next spraying cycle.

At the beginning of the spraying, the lever 3 which is mechanicallyconnected to the rotary valve 2 for the respective resin components ispushed to the open position. Thus, connections Al, A2 are opened betweentubes for resin components and the mixing chamber 6 as well as aconnection for servo air to a relay for ventilating the mixing motor 4,which has started immediately. At the same time, a relay 14 which closesthe circuit to an electric motor 15, which via speed variators run twodosing pumps 16 is ventilated, whereby the electric motor starts. Theservo air also is used for actuating a reversing valve 9 whichventilates a piston in a compressed air cylinder 10, with the pistonwhich is mechanically connected to a liquid piston pump 11 therebymaking a linear motion so that the cleaning liquid is drawn into theliquid pump. Finally, the connection A3, distributing air for atomizingthe media is opened. Two resin components now flow from the respectivedosing pumps 16 through tubes into the mixing chamber 6 wherein they arehomogenized by means of rotating and fixed members. The materialthereupon passes through an opening 5 to a spray nozzle in whichatomizing and spraying of the material takes place. Due to the limitedvolume of the mixing chamber, the material turn-over will be so greatthat there is no risk for polymerization of a higher degree as long asthe spraying operation is continued.

At the end of the spraying, the lever 3 is pushed to the shut or closedposition, whereby the direct connections for resin components A1, A2 andatomizing air B3 through the rotary valves 2 are stopped. At the sametime, the relay 14 for the pump motor 15 is purged, so that the pumpmotor stops and the distribution of resin components ends. The reversingvalve 9 to the air cylinder 10 of the cleaning liquid pump 11 is purged,and the valve slide, due to spring actuation, is carried to its originalposition in which the air cylinder piston is ventilated. The cleaningfluid, which earlier has been drawn in thereby is emitted from theconnected liquid pump to the mixing chamber 6 with an increased pressuredepending on the difference in area between the air piston and the pumppiston. Non-return valves 12, 13 are arranged in a conventional manneron the liquid pump 11 in order to make in-and-out-pumping possible'. Bymeans of a delay arrangement 17, the mixing motor 4 continues to rotatesome seconds after the cleaning has taken place in order to make thecleaning more efficient.

What is claimed is: p

1.. In a machine for spraying plastics, a mixing head having a mixingchamber, said mixing chamber being connected to a plurality of spraynozzles, two rotary valves in the mixing chamber, said valves being me.-chanically. connected and operated manually by a common lever, twodosing pumps for supplying resin components, a source of pressurized airfor atomizing the resin mixture, the valves in one position providingconnections between the mixing chamber and the dosing pumps and betweenthe mixing lchamber and the source of pressurized air, a cleaning liquidpump, an air cylinder provided with a piston mechanically connected tothe cleaning liquid pump, a conduit between the pressure side of thecleaning liquid pump and the mixing chamber, one of the valves in saidone position further connecting the source of pressurized air with areversing valve to maintain the position of such valve, said one valvebeing designed to connect the source of pressurized air with one of theends of the air cylinder, the valves in a second position connecting thecleaning liquid pump with the mixing chambers, closing the connectionsfor resin components and atomizing air, disconnecting the connectionbetween the source of pressurized air and the reversing valve andpurging the conduit therebetween thus causing the reversing valve toswitch to a position to initiate a cleaning cycle in which the cleaningliquid pump forces liquid through the mixing chamber.

2. The machine as claimed in claim 1 including a pneumatic mixingmotorin the mixing head to assist the mixing by stirringthe resin components,said motor being fed by a conduit from the source of pressurized air,said conduit having a valve governed by the reversing valve, and a delaycircuit provided between the reversing valve and the mixing motorfeeding valve to maintain the connection between the motor and source ofpressurized air open during at least a part of the cleaning cycle.

1. In a machine for spraying plastics, a mixing head having a mixingchamber, said mixing chamber being connected to a plurality of spraynozzles, two rotary valves in the mixing chamber, said valves beingmechanically connected and operated manually by a common lever, twodosing pumps for supplying resin components, a source of pressurized airfor atomizing the resin mixture, the valves in one position providingconnections between the mixing chamber and the dosing pumps and betweenthe mixing lchamber and the source of pressurized air, a cleaning liquidpump, an air cylinder provided with a piston mechanically connected tothe cleaning liquid pump, a conduit between the pressure side of thecleaning liquid pump and the mixing chamber, one of the valves in saidone position further connecting the source of pressurized air with areversing valve to maintain the position of such valve, said one valvebeing designed to connect the source of pressurized air with one of theends of the air cylinder, the valves in a second position connecting thecleaning liquid pump with the mixing chambers, closing the connectionsfor resin components and atomizing air, disconnecting the connectionbetween the source of pressurized air and the reversing valve andpurging the conduit therebetween thus causing the reversing valve toswitch to a position to initiate a cleaning cycle in which the cleaningliquid pump forces liquid through the mixing chamber.
 2. The machine asclaimed in claim 1 including a pneumatic mixing motor in the mixing headto assist the mixing by stirring the resin components, said motor beingfed by a conduit from the source of pressurized air, said conduit havinga valve governed by the reversing valve, and a delay circuit providedbetween the reversing valve and the mixing motor feeding valve tomaintain the connection between the motor and source of pressurized airopen during at least a part of the cleaning cycle.